The long term goals of the proposed research are to determine the role of carotenoid pigments in cyto-protection of the plant pathogenic smut fungus Ustilago violacea and to use U. violacea in developing a eukaryotic screening system for assessing the general value of carotenes for protection against the effects of toxic, mutagenic and carcinogenic agents. The project will make health related contributions in providing an initial means to identify cancerous and mutagenic agents that can be potentially protected against by carotenoid pigments in higher eukaryotes including man, and in contributing to the scientific training of undergraduates interested in health related professions. Additional contributions will be made in the areas of fungal physiology and photobiology. The specific aims of this project are to test several hypotheses relating cellular carotene content to cyto-protection in U. violacea. Specifically the project will address the following major objectives: 1.) Determine the extent of carotene protection in response to the toxic effects of various radiation sources and chemicals, 2.) Determine the extent of carotene related protection from DNA damage as measured by the induction of mitotic recombination and mutation in response to various radiation sources and chemicals, 3.) Develop a rapid reproducible test for assessing the extent of carotene related cyto-protection in response to any cyto-toxic, mutagenic or carcinogenic agent. The experimental procedures involve the study of survivial, auxotrophic mutational reversion and mitotic recombination in related haploid and diploid strains of U. violacea with genetically defined carotene compositions in response to UV and visible radiation, hydrogen peroxide, nitrogen mustard, cyclophosphamide and dimethyl-benz-a-anthracene. The procedures are straight forward and well documented. This in addition to the results of our preliminary studies provide assurance that the experiments can be completed with little difficulty.